Your positioning skill. Use this early game to place an enemy behind or in range of a tower for a simple kill. Late game, this skill is used for saving, positioning, (if you are greedy) last hits and general LULZ.

Your laning ability. 2 levels of this first up will ensure you and your team mate a long lasting lane partnership. This can also be used to save and can be the deadly difference between someone being killed from ignite and surviving with 1 health. This move also creates creep pushes when used often.

Your tanking ability. This is one of Alistar's greatest abilities. Almost invincibility, huge attack damage and cleanse all in one. This skill should be used after initiating, or to save your life. On minor cases, this skill can be used when 1v1 to buff up your fists a little.

Skill Build

Introduction

We have all seen Alistar's enter the game, and to be honest, most of them have sucked bad. Well today I am going to tell you my build and play style, and really show you how this "sucky" tank can be the greatest thing to happen to your team. In this guide I will tell you about, Stunning and Butting, Saving your ally, lane control, and munching towers.

So sit back and enjoy my first guide!

Summoner Abilities

The Duo I use is: Flash + Exhaust
This combo enables you to flash/pulverize, then exhaust the unsuspecting victim while your carry gets fed.
Other recommended abilities: Ghost
Ghost is good for escaping but can be useless at times, flash over ghost walk any day. Cleanse
Good if there is a lot of CC going on, but your ulti already has cleanse so only use when not confident or against a team full of CC Teleport
Teleport if you plan on farming, but really not a huge input to the team.

Never get these: Revive
The most useless summoner ability in the game. I don't even need to explain. Ignite
You are a support tank, ignite is useless on you.

Items

This really splits a noob Alistar from a brilliant Alistar. In my experience I have seen many people buy AD/AP/AS items. Now I am biased, but this is all wrong. Alistar is a support tank, his abilities don't argue with this fact. If Alistar was supposed to damage a lot, headbutt would have a shorter knock back, pulverize would stun longer and his ultimate would have nuke/slow instead of near invincibility/damage.
Now that I have had my rant, lets look at some items.

Alistar's items are very dependent on your playing situation.

Boots:
My boots of choice are Boots of Swiftness
Works in great synergy with swiftness runes. This also allows you too catch up and pulverize an enemy while your carries lag behind. Ninja Tabi
Get these if you are versing Champs like Jax and Xin. This can often reduce their damage more than you really realize. Mercury's Treads
Get these if you are versing a lot of magic and CC abusers. Champs like Ryze and Veigar hate these boots.

Core Build(Physical Team): Ninja Tabi Warmog's Armor Sunfire Cape Randuin's Omen Thornmail
Items Explained:
Boots are obvious. Warmog's, this item gives great health and regen. As a benefit, it increases with assists/creep kills. Sunfire cape, This item gives some nice armor and health and BURNS the enemy when they come near. Good for pushing. Randuin's, Good health, decent armor but amazing slow. Good for slowing runners and halting fast attackers. Thornmail, When focused, this really plays with Jax and fast attackers heads alike. This is a must if all the team is physical.

Core Build(Magic Team): Mercury's Treads Banshee's Veil[item=Force of Nature] Chalice of Harmony Guardian Angel Hexdrinker
Items Explained:
Boots are obvious. Banshee's Veil, Great magic resistance, little buff of health and mana, and an awesome aura. Force of Nature, Awesome magic resistance, Awesome health regen (both item and passive) and a nice buff to movement speed. Chalice of Harmony, nice magic resistance, the main purpose of this item is the keep your mana pool lasting all game. Guardian Angel, both armor and magic resistance, also allows you to come back and pulverize once more. Hexdrinker, your life saver in some cases, little bit of AD and magic resistance, but the passive shield makes this item essential.

A lot of people argue that A good Alistar should be specified purely into defense. In my opinion the defense tab gives very little defensive effect to you. I would rather the 6% or so reduction in cool down, then 4% damage reduction.

Runes:

Well my runes are set out to help you in different time of the game. So I will go through them individually. Greater Mark of Fortitude
Greater Mark of Fortitude is here to give you an early boost in the game. 9x3.47= 31.23hp Which is a nice little boost for the early game skirmishes that go on throughout the first 5 or so minutes. Greater Seal of Focus
Greater Seal of Focus is really for all round game. 9x0.28%=2.52% cooldown Reduction. This works in perfect synergy with the mastery build. Greater Glyph of Replenishment
Greater Glyph of Replenishment is an all round glyph for Alistar. At the start it makes sure you have enough mana to spam heal and now and then pop Pulverize, and at the end it makes you able to heal everyone and keep everyone laned without mana worries. Greater Quintessence of Swiftness or Greater Quintessence of Defense
I use swiftness, it helps more than you can imagine when attempting your Pulverize+Headbutt combo. If you are not too comfortable with Alistar I recommend defense.

Pro's and Con's

Pro's:
+Great Initiating.
+You will piss a lot of people off
+Tower's can't matador around you... (you own them)
+Uber CC
+Love from your teammates
+Lane staying/ Life saving

Your Role in the Team

As a support tank, it is your responsibility to start fights, heal, spam CC and when it call for it, die.

Initiator/Tank
You can initiate by flashing and pulverizing. Once all stunned position yourself to knock back their strongest carry to your teammates. Activate your ultimate, spam heal, continue to stun, your team should do the rest.

Tower Tanker.
You will also be expected to tank a few towers. With your passive, this is simple. If you get low, pop the ult, not only will it take the tower down quicker, but the tower will no longer damage you.

Life Saver.
This means running with your carry and headbutting/stunning chasers to keep them away from your carry. Whilst not stunning/butting spam your heal next to your carry. This position a lot of the times means your demise, although as a support tank, it is your job.

Pusher.
This is simple and should be done without thought. Lane, heal your creeps and attack theirs. When the tower comes around, heal your creeps and munch on that tower.

Ganker.
Similar to Initiator, While ganking, you go behind the enemy whilst your carry initiates. Stunning and butting them. When they run, run ahead and use Randuin's slow to let the rest catch up. If needed, butt/stun.

Conclusion

In all, Alistar is easily one of the greatest tanks. The lack of experience with him makes people think he is noob/underpowered. In truth, Alistar is one of the most unused champs in the game and is shadowed by those who attempt to DPS with him and Fail. Thanks for reading my guide, May the horns be with you.